What Is Image Alt Text?

Understanding the Role of Alt Text on Your Website

So much of the web is visual. We communicate with photos, charts, and illustrations. But what happens when that visual information is lost? A small piece of code, known as alt text, bridges this gap for both people and technology, ensuring nothing gets lost in translation.

So, what is alt text? At its core, it is a written description of an image that you place within your website’s HTML code. While you might hear it called an "alt tag," its proper name is the "alt attribute," and it lives inside an image tag (``). Its most fundamental job is to act as a backup. We have all visited a page where a picture was supposed to be, but all we saw was a broken image icon. When that happens, the browser displays the alt text instead. This ensures your message still gets across, even when a slow connection or a technical glitch gets in the way.

Think of it like a caption written on the back of a printed photograph. If you could only feel the outline of the photo paper, that short description on the back would give you all the context you need. It offers a quick, clear explanation for anyone or anything that cannot see the front. This simple function is the foundation of alt text, but its purpose extends far beyond just fixing broken images.

Making Your Visual Content Accessible to Everyone

Moving beyond the technical function, we arrive at the most important reason for using alt text: making your website accessible to everyone. Millions of people with visual impairments use screen reader software to browse the internet. This technology converts the content on a webpage, from headings to paragraphs, into spoken words.

When a screen reader encounters an image, it looks for the alt text and reads it aloud. A well-written description provides the listener with the same context a sighted user would get from looking at the picture. Now, imagine the alternative. If an image has no alt text, the screen reader might announce a generic word like "image" or, even worse, a confusing file name like "IMG_4077.jpeg." This leaves the user with a gap in their experience, excluding them from a piece of the story you are trying to tell.

Writing descriptive alt text is a direct and powerful way to practice digital inclusivity. It ensures every visitor, regardless of their ability, can have an equivalent experience on your site. This is not just a kind gesture; it is a core principle of good web design. This practice aligns with established standards like the Web Content Accessibility Guidelines (WCAG). As the official W3C documentation on image accessibility guidelines explains, providing text alternatives for non-text content is fundamental to creating a more equitable web for all users. It transforms a technical task into an act of empathy.

Helping Search Engines Understand Your Images

With an inclusive foundation in place, you can also see how alt text delivers a significant business benefit. Search engines like Google are incredibly advanced, but they cannot "see" an image the way a person does. They rely on the text surrounding an image, including its alt text, to understand what it contains and why it is relevant.

Think of alt text for SEO as a direct signal you send to search engine crawlers. It gives them the context needed to index your image correctly, allowing it to appear in image search results. This practice also reinforces your page's overall topic. If you have an article about baking sourdough bread and your images have alt text like "baker scoring a sourdough loaf before baking," you are strengthening the page's authority on that subject. As HubSpot reports, images appear in a significant portion of Google search results, highlighting the traffic potential you unlock with good descriptions.

This data becomes even more critical as technology evolves. Search engines increasingly use sophisticated systems to process information, and providing clear data points like alt text is crucial for how advanced AI and data analytics solutions interpret and rank web content. By clearly labeling your images, you are feeding these systems the structured data they need to favor your content. This is just one piece of a much larger puzzle, and you can learn more about the new layers of SEO that every blogger should know to stay ahead.

How to Write Clear and Effective Alt Text

Understanding the "why" is one thing, but knowing how to write alt text effectively is what puts that knowledge into practice. It is less about complex rules and more about being clear and helpful. Following a few alt text best practices will ensure your images are useful for both people and search engines.

1. Be Specific and Descriptive
   Describe the image as if you were explaining it to someone over the phone. Your goal is to paint a picture with words. Instead of writing "dog," a more effective description would be "black Labrador puppy playing with a yellow tennis ball on the grass." The first is accurate but unhelpful; the second provides genuine context and detail.
2. Keep It Concise
   While detail is important, you should also be brief. Aim for a length of around 125 characters or less. The practical reason for this is that many screen readers stop reading after this point. You want to make sure the most critical information is delivered first, so get straight to the point without unnecessary words.
3. Use Keywords Naturally
   If your target keyword genuinely describes the image, feel free to include it. For example, if your article is about "indoor plant care," an alt text like "person watering a fiddle leaf fig in a white ceramic pot" is perfect. However, you must avoid "keyword stuffing" by forcing in irrelevant terms. Writing "plant indoor plant care green plant houseplant" creates a terrible experience for screen reader users and can be penalized by search engines.
4. Avoid Redundant Phrases
   Never start your alt text with "Image of..." or "Picture of..." Screen readers already announce that the element is an image, so including these phrases is repetitive. It is like saying, "This is a sentence that I am saying." Just jump straight into the description to provide a smoother, more efficient experience for the user.

Distinguishing Between Image Types

As you get more comfortable writing alt text, you will realize that not all images should be treated the same. The right approach depends on the image's purpose on the page. Understanding the difference between decorative vs informative images is key to getting it right. Let’s break down the main categories.

Informative Images

These are images that convey important information and add context to the content. Examples include a product photo on an e-commerce site, a headshot of an author, or a chart showing data. For these images, you must write a specific, descriptive alt text that communicates what the image shows.

Functional Images

These are images that perform an action. The most common examples are icons used inside links or buttons, such as a magnifying glass for a search function or a shopping cart icon. For functional images, the alt text should describe the action or destination, not the image itself. For a magnifying glass icon, the alt text should be "Search," not "magnifying glass."

Decorative Images

These are visuals that exist purely for stylistic purposes. They add no new information and are there only to make the page look better. Examples include abstract background patterns, ornamental borders, or stylistic dividers. For these images, you should use an empty alt attribute (`alt=""`). This tells screen readers to ignore the image completely, which is the correct and intended behavior. It prevents the user from being interrupted by unhelpful announcements like "blue swirly line."

How to Handle Different Image Types

Image Type	Purpose	Example	Alt Text Rule
Informative	Conveys information or context	A graph showing quarterly sales	Describe what the graph shows
Functional	Performs an action	A shopping cart icon in a button	Describe the action (e.g., 'Go to cart')
Decorative	Adds visual style only	An ornamental border on the page	Use an empty alt attribute (`alt=""`)

Common Alt Text Mistakes You Should Avoid

Mastering alt text is often about avoiding a few common pitfalls. Once you learn to spot these mistakes, you will be well on your way to creating a more accessible and effective website. Here is a final checklist of what not to do.

• Omitting Alt Text Entirely: Leaving the alt attribute empty on an informative image makes it invisible to screen reader users and search engines. It is a missed opportunity for both accessibility and visibility.
• Using Generic File Names: Never let your content management system auto-populate alt text with a useless file name like `IMG_8021.jpg`. This provides zero context and just creates noise for screen reader users.
• Writing Vague Descriptions: Alt text like "photo" or "graphic" is as unhelpful as no alt text at all. Always aim to provide meaningful information that adds value.
• Stuffing with Keywords: Remember that alt text is for humans first. Forcing in a string of keywords creates a jarring, robotic experience for screen reader users and can be viewed negatively by search engines.

Getting these fundamentals right is a key step in building a better website. For more insights on creating high-quality content, you can explore additional resources on our blog.